Oral dosage form

ABSTRACT

The present invention in general relates to a pharmaceutical dosage form comprising one or more granules, and a method for manufacturing thereof. The granules of the dosage form are prepared via the extrusion/spheronization technique using partially hydrolysed polyvinyl alcohol. These granules have the advantage that a high drug load can be contained therein.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/087,835, filed Sep. 24, 2018, which is a U.S. National Stage Entryunder 35 U.S.C. § 371 of PCT/EP2017/057063, filed Mar. 24, 2017, whichclaims priority to EP 1616249.1, filed Mar. 25, 2016, the contents ofwhich are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention in general relates to a pharmaceutical dosage formcomprising one or more granules, and a method for manufacturing thereof.The granules of the dosage form are prepared via theextrusion/spheronization technique using partially hydrolysed polyvinylalcohol. These granules have the advantage that a high drug load can becontained therein.

BACKGROUND TO THE INVENTION

Multiparticulate drug delivery systems (e.g. pellets/granules) arebecoming more important due to their distinct advantages compared tosingle unit systems, such as reproducible and generally shortgastric/intestinal residence time, flexibility to blend pellets withdifferent compositions or release patterns (personalized medicines), anddecreased risk of dose dumping (Dukic-Ott et al., 2007). Pellets, whichare defined in pharmaceutical industry as small (between 0.5 and 2.00mm), free-flowing, spherical particles, can be obtained by solution orsuspension layering of cores, powder layering, spray congealing, meltspheronisation or extrusion/spheronisation (Lustig-Gustafsson et al.,1999). Extrusion/spheronisation is the most popular pelletisationtechnique and is suitable to produce pellets with extended releaseprofile. However, this technique requires the production of a cohesivewet mass which does not adhere to the extruder and retains some degreeof rigidity. Furthermore, the extrudates need to be brittle enough tobreak into smaller extrudates and contain some degree of plasticity todeform into spheres (Swarbrick, 2006). As most drug molecules do notexhibit these characteristics, microcrystalline cellulose (MCC) isconventionally used as excipient to obtain formulations with sufficientrigidity, plasticity and water absorbing capacity. However, the use ofMCC has some disadvantages, such as higher batch-to-batch variabilitydue to its natural origin, increased disintegration time,incompatibility with certain drug molecules (Basit et al., 1999).Furthermore, the drug load in MCC based pellets is limited (Mallipeddiet al., 2010), which restricted the use of those pellets in fixed dosecombinations, whereby two or more drugs are combined inside the pellets.Combination drug therapy is recommended for elderly and long-term carepatients in order to facilitate patient compliance (Raffa, 2001).Therefore, several alternatives such as biopolymers (i.e. starch,chitosan) or synthetic polymers (i.e. hydroxypropyl methylcellulose,polyethylene oxide) are proposed in order to decrease MCC concentrationin the pellets. However, these materials have inferior properties (e.g.,less water holding capacity, ionic polymers require granulation liquidwith a specific pH) for extrusion/spheronisation, compared to MCC(Dukic-Ott et al., 2009).

In an attempt to provide a solution to the above mentioned problems withthe currently used extrusion aids (e.g. MCC), the present invention hasdemonstrated for the first time that inclusion of partially hydrolyzedpolyvinyl alcohol in granules allows to manufacture oral dosage formswith a high drug load.

Partially hydrolysed polyvinyl alcohol (PVOH; PVA) is a water-solublesynthetic polymer produced by polymerisation of vinyl acetate followedby partial hydrolysis and therefore several grades with different degreeof polymerization and hydrolysis are available. Pharmaceutical gradesPVOH are mainly partially hydrolysed and are currently used inpharmaceutical applications as stabilizing or viscosity-increasingagent, and are often used in the preparation of coating layers ofpharmaceutical pellets or tablets (EP0468247, US2010062062,Araujo-Junior et al., 2012). Partially hydrolysed PVOH was alsoevaluated for processing in hot melt extrusion but here again onlyformulations with low drug load could be produced (De Jaeghere W et al.,2015).

SUMMARY OF THE INVENTION

The present invention thus provides granules that can be utilized in amultiparticulate dosage form that provides rapid, sustainend and/orcontrolled release of a drug from the dosage form, particularly when thedosage form is orally administered. The dosage form has the advantagethat a high drug load can be contained.

The present invention relates to a pharmaceutical dosage form orformulation comprising one or more granules having a core and optionallya coat; wherein said core comprises at least one active agent, partiallyhydrolyzed polyvinylalcohol (PVOH) and a diluent, in particularmicrocrystalline cellulose (MCC). In particular, the granule is anextrudate. Even more in particular, the granule is prepared via anextrusion and/or spheronization process, hence in said embodiment thedosage form comprises one or more extruded and/or spheronized granules.The partially hydrolyzed PVOH is a copolymer of vinyl alcohol and vinylacetate, having a degree of hydrolysis between 30 and 95%, moreparticular between 70 and 95% and even more particular between about 70and about 90%. In a specific embodiment, the partially hydrolyzed PVOHis present at an amount varying between and about 1 and 20% by weight ofthe core of the particle; more in particular between about 1 and 15% byweight of the core of the particle. The diluent (specifically the MCC)is generally present at an amount of between and about 1 and 30% byweight of the core of the particle. Furthermore, the active agent ispresent at an amount of at least 50% by weight of the core of theparticle. Typically, the granule is substantially spherical and has adiameter in the range of about 0.3 to about 3 mm.

In a further embodiment, the dosage form of the present invention is amultiparticulate dosage form or composition (e.g. a tablet, capsule orunit-dose), formulated as an oral dosage form and especially suitablefor the immediate, controlled and/or sustained release of one, two ormore active agents. Optionally, a pharmaceutically acceptable excipient,a further diluent and/or carrier can be added to the composition.

In a further embodiment, the granule further comprises at least onecoating layer, talc layer and/or taste-masking layer, in particular acoating layer comprising a suitable polymer, such as e.g. anacrylic-based polymer.

The present invention further encompasses the dosage form or compositionof the present invention for use as a veterinary or human medicine and amethod for the release of one or more active agents comprising orallyadministering to a subject said dosage form or composition.

A particular method of preparing a granule in accordance with thepresent invention comprises the steps of:

mixing an active agent, partially hydrolyzed polyvinyl alcohol and adiluent;

wetting the mixture;

extruding the wet mixture to obtain an extrudate;

spheronizing the extrudate to obtain a plurality of substantiallyspherical granules; and

drying the granules.

PVOH can be added as a dry powder or as an aqueous solution. Optionally,the method further comprises a coating step (after the drying step). Theinvention also comprises the granules obtained by the method asdescribed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: Particle size distributions (mean±standard deviation, n=3) offormulations containing 70% drug (Form. 2 (▪), 3 (▴), 4 (●)), 80% drug(Form. 7 (▪), 8 (▴), 9 (●)) or 90% drug (Form. 14 (▪), 15 (▴)) and PVOH.PVOH was added either in dry powder form (closed symbol) or as aqueousdispersion (open symbol). MCC pellets were used as reference (X).

FIG. 2: Aspect ratio and sphericity (mean±SD, n=3) of formulations as afunction of particle size (

D10,

50 and

D90), PVA/MCC ratio (5/95—20/80%) and drug load (70-90%). PVA was addedeither dry (d) or wet (w). MCC pellets without drug were used asreference (Ref.). Sieve fraction 710-1000 μm was used (n=3).

FIG. 3: A. In vitro dissolution profiles (mean±standard deviation, n=3)of pellets with different acetaminophen concentration: Formulations 4, 9and 14 containing 70%, 80% and 90% drug, respectively. PVOH was addedeither in dry powder form (▪) or as aqueous dispersion (▴). MCC pelletswithout PVOH containing 50% acetaminophen were used as reference (X). B.Mean in vitro dissolution profiles (±SD, n=3) of metformin.HCl pelletswith different coating levels ((▪) 0, (▴) 8, (▾) 14 and (●) 20% (w/w))and (*) Glucophage™ SR 500 (½ tablet) reference.

FIG. 4: Aspect ratio (AR) and sphericity (mean±standard deviation, n=3)of formulations containing 70% drug. Acetaminophen (Acet.) or anacetaminophen/tramadol.HCl mixture (62.8/7.2) (Acet./Tram.) was includedas drug in the pellets. MCC pellets without drug were used as reference(Ref.). The 710-1000 μm sieve fraction was used for analysis (n=3).

FIG. 5: In vitro dissolution profiles (mean±standard deviation, n=3) ofacetaminophen (▴) and tramadol.HCl (▪) from acetaminophen/tramadol.HClpellets.

FIG. 6: Mean plasma concentration-time profiles (±SD, n=6) after oraladministration of 250 mg Metformin.HCl to beagle dogs: (●) coated PVApellets (F24) and (*) Glucophage™ SR 500 (½ tablet).

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the singular forms “a”, “an”, and “the” include pluralreferents unless the context clearly dictates otherwise. The terms“comprising”, “comprises” and “comprised of” as used herein aresynonymous with “including”, “includes” or “containing”, “contains”, andare inclusive or open-ended and do not exclude additional, non-recitedmembers, elements or method steps. The term “about” as used herein whenreferring to a measurable value such as a parameter, an amount, atemporal duration, and the like, is meant to encompass variations of+/−10% or less, preferably +1-5% or less, more preferably +/−1% or lessof and from the specified value, insofar such variations are appropriateto perform in the disclosed invention. It is to be understood that thevalue to which the modifier “about” refers is itself also specifically,and preferably, disclosed. Whereas the terms “one or more” or “at leastone”, such as one or more or at least one member(s) of a group ofmembers, is clear per se, by means of further exemplification, the termencompasses inter alia a reference to any one of said members, or to anytwo or more of said members, such as, e.g., any >3, >4, >5, >6 or >7etc. of said members, and up to all said members. All references, andteachings specifically referred to, cited in the present specificationare hereby incorporated by reference in their entirety. Unless otherwisedefined, all terms used in disclosing the invention, including technicaland scientific terms, have the meaning as commonly understood by one ofordinary skill in the art to which this invention belongs. By means offurther guidance, term definitions are included to better appreciate theteaching of the present invention. In the following passages, differentaspects of the invention are defined in more detail. Each aspect sodefined may be combined with any other aspect or aspects unless clearlyindicated to the contrary. In particular, any feature indicated as beingpreferred or advantageous may be combined with any other feature orfeatures indicated as being preferred or advantageous. Referencethroughout this specification to “one embodiment” or “an embodiment”means that a particular feature, structure or characteristic describedin connection with the embodiment is included in at least one embodimentof the present invention.

The present invention provides a wet mass formulation with the desiredcharacteristics for both extrusion and spheronization; in particular forcold extrusion (i.e. extrusion at room temperature or near roomtemperature; typically between about 10° C. and about 40 or 50° C.).More specific, the mass is plastic enough to be extruded through thefine pores of an extruder and does not crumble apart. At the same time,the extrudates obtained from the formulation are sufficiently brittle sothat they may be broken apart and spheronized in a spheronizer. Hencethere is an optimal balance between the two desired properties i.e.plasticity and brittleness.

The present invention has demonstrated for the first time that inclusionof polyvinyl alcohol allows manufacturing granules, more particularspherical granules such as pellets, using formulations with a high drugload. Moreover, said granules provide the characteristics that aredesirable for the oral administration of drugs. It was furtherdemonstrated that these formulations have the desired balance ofplasticity and brittleness and are hence particularly useful inmanufacturing granules via extrusion and spheronization; in particularvia cold extrusion.

In one embodiment, the present invention provides a spherical particlecomprising (a combination of) at least one active ingredient, partiallyhydrolyzed polyvinylalcohol (PVOH) and a diluent, preferablymicrocrystalline cellulose (MCC). In particular, the at least one activeingredient, partially hydrolyzed polyvinylalcohol (PVOH) and diluent arepresent in the core of the particle.

The term “granules” as used herein means free-flowing particles with anarrow size distribution, typically varying between 0.5 and 3 mm in sizefor pharmaceutical applications. Spherical granules are also referred toas pellets. Typically they are formed as a result of a pelletizationprocess resulting into small, free-flowing, spherical or semi-sphericalunits. Pellets, being multiple unit-dosage forms, are widely used asthey offer both manufacturing and therapeutic advantages oversingle-unit solid dosage forms. There are different techniquesapplicable for the production of pellets in pharmaceutical industries.In the present invention, the granules/pellets have a diameterpreferably ranging from about 0.3 to about 3.0 mm, more preferably fromabout 0.5 to 2.0 mm, even more preferably from 0.7 to 1.5 mm, and mostpreferably from 0.8 to 1.2 mm.

“Partially hydrolyzed polyvinyl alcohol (PVOH; PVA; general formula[CH₂CH(OH)]_(n))”, used for pharmaceutical applications, is a copolymerof vinyl acetate (CH₃CO₂CHCH₂) and vinyl alcohol (CH₂CHOH). Polyvinylacetate is a water-insoluble polymer which is obtained by polymerizationof vinyl acetate. This polymer is used for the production of polyvinylalcohol by hydrolysis or alcoholysis to remove the acetyl groups frompolyvinyl acetate. This removal of acetyl groups may be carried out topartial completion so as to give a product which is a copolymer of vinylalcohol and vinyl acetate. If vinyl alcohol predominates, but there isstill a substantial quantity of vinyl acetate present, such a copolymeris soluble in cold water and is frequently referred to as “partiallyhydrolyzed” polyvinyl alcohol. The residual vinyl acetate content istypically about 11 wt % corresponding to about 12 mol %. If the reactionis taken further, close to completion, the crystallinity of thepolyvinyl alcohol increases and the solubility in cold water decreasesvery markedly. Material of this type is referred to as “fullyhydrolyzed” polyvinyl alcohol. Its content of residual vinyl acetate istypically no greater than 3 mol %.

Several polyvinyl alcohol grades are commercially available. They mainlydiffer in molecular weight and residual content of acetyl groups (i.e.degree of hydrolysis). Different commercially available PVOH grades arelisted herein and can be used in the embodiments of the presentinvention.

Degree of hydrolysis Pharmaceutical PVOH grade Mw (mol %) grade?Partially hydrolysed PVA 5-05 38,000 72.5-74.5 no PVA4-88 31,00086.7-88.7 yes PVA5-88 39,000 86.7-88.7 yes PVA8-88 67,000 86.7-88.7 yesPVA18-88 130,000 86.7-88.7 yes PVA26-88 183,000 86.7-88.7 yes PVA40-88205,000 86.7-88.7 yes Fully hydrolysed PVA4-98 27,000 99.0-99.8 yesPVA28-99 145,000 99.0-99.8 Limited to JPE

Fully hydrolysed PVOH grades are only slightly soluble in water.Therefore, the ability to add enough PVOH via the wet addition method islimited, making it impossible to achieve high drug loaded pellets withgood quality attributes. Partially hydrolysed polyvinyl alcohol arecompletely soluble. Based on their high aqueous solubility, these gradeswere evaluated for their potency as a pelletisation aid (via liquidaddition method).

The preferred soluble polymer is partially hydrolyzed polyvinyl alcohol.As already mentioned above this is a copolymer of polyvinyl alcohol withvinyl acetate. Generally these copolymers are hydrolyzed to an extentbetween 30 and 95 mol %, more commonly between 50 and 95 mol %, inparticular between 60 and 95 mol %, even more in particular between 70and 95 mol %, and most particular between about 70 and 90 mol %. Thus,the mole ratio of vinyl alcohol to vinyl acetate lies between 30:70 and95:5, preferably between 40:60 and 90:10. Partially hydrolyzed polyvinylalcohol is fully biodegradable. The skilled person will be aware thatdepending on the water content and the type and/or concentration of theAPI in the core of the granule, the amount of PVOH can vary. In aspecific embodiment, the granule core comprises up to 30 wt.% ofpartially hydrolyzed PVOH, preferably up to 20 wt. %, more preferably upto 14 wt. %, even more preferably up to and including 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12 or 13 wt. %, and more in particular about and between0,5 and 20 wt.% of PVOH, preferably about and between 1 and 15 wt. % ofPVOH, more preferably about and between 1 and 10 wt. % of PVOH,including all values in between.

As used herein, a “diluent” is a diluting agent, which is waterinsoluble, and has a large water absorption and retention capacity.Suitable diluents useful in the present invention include biopolymers,such as powered cellulose, starch (derivatives), chitosan,κ-carrageenam, pectinic acid; (semi-)synthetic polymers, such ashydroxypropyl methylcellulose, hydroxyethyl cellulose, polyethyleneoxide, cross-linked polyvinylpyrrolidone; and other materials such asglyceryl monostearate. In a preferred embodiment, the diluent ismicrocrystalline cellulose. “Microcrystalline cellulose” (MCC), inparticular a pharmaceutical grade thereof, is well known in the art ofpharmaceutical industry for its high surface porosity and itsoutstanding capillary character. It is available from a variety ofcommercial sources, e.g. Avicel® PH101 (commercially available from FMCCorporation, Philadelphia, Pennsylvania), Emcocel® (Mendell), Vivocel®(JRS), and the like. Microcrystalline cellulose is a partially purifieddepolymerized form of cellulose and is obtained by treating pulpsderived from fibrous plant material with mineral acid. The acidpreferentially attacks the less ordered or amorphous regions of thecellulose polymer chain, thereby exposing and freeing the crystallinesites which form cellulose crystallite aggregates. The reaction mixtureis washed to remove the degraded byproducts, the resulting wetcake isfreed of water and the dried cellulose crystallite aggregates, or morecommonly MCC, recovered. MCC is a white, odorless, tasteless, relativelyfree-flowing powder, insoluble in water, organic solvents, dilutealkalies and dilute acids. In a specific embodiment, the core of thegranule of the present invention may comprise up to 40 wt. % of adiluent, in particular MCC, more specific about and between 0 and 40 wt.% of diluent, even more specific between 0.5 and 35 wt. %, andpreferably between 1 and 30 wt. % diluent, more preferred between 5 and25 wt. % and even more preferred between 5 and 20 wt. % diluent,including all values in between.

The ratio PVOH/MCC within the core of the granule generally depends onthe concentration of the API (and optionally the water content) and canreadily be determined by the skilled person. In a particular embodiment,the PVOH/MCC ratio in the core of the granule or pellet is 50/50, butpreferably about or within the range 45/55 and 1/99, such as e.g. 40/60,30/70, 20/80, 10/90 or 5/95, including the ratios in between. Ingeneral, the ratio PVOH/MCC will increase with increasing drugconcentration in the granule.

In a specific embodiment, the pharmaceutical dosage form or morespecifically the core of the granules of the present invention do notcontain any plasticizer, such as but not limited to polyethylene glycol,glycerol and sorbitol.

The active ingredient(s), partially hydrolyzed polyvinylalcohol (PVOH)and the diluent, such as MCC, form the “core” of the pellet. Thegranules may be used as they are, or optionally, a coating material maybe applied, preferably by means of the film-coating process, to thegranules. The granules may be coated for one or more functional purposeswhich include, without limitation, for further controlling the releaseproperties of the active agent, for taste masking, for impartingresistance to gastric fluid, and to improve the shelf-life. Film coatinginvolves the deposition, usually by spraying, of a thin film of polymersurrounding the granule core. The coating solution contains a polymer ina suitable liquid solvent and optionally mixed together with otheringredients such as plasticizers, pigments and/or colorants. Afterspraying, the drying conditions permit to remove substantially all ofthe solvent.

The particular coating material used is not critical to the presentinvention, and depends upon the purpose of the coating material, e. g.the release profile, taste-masking, the ability to stay intact and/or towithstand the mechanical stress of compaction without cracking and soon. Non-limiting examples of coating polymers useful for controlling therelease properties of the active agent and/or taste masking are wellknown in the art and include derivatives of cellulose such asmethylcellulose, hydroxypropylmethylcellulose and ethylcellulose,polyvinylpyrrolidone and aminoalkylmethylacrylate copolymers. Examplesof coating polymers useful for imparting resistance to gastric fluidinclude shellac, cellulose acetate phthalate, polyvinylacetate,hydroxypropyl methylcellulose acetate succinate, polyvinyl acetatephthalate (PVAP) styrene/acrylic acid copolymers, methacrylic acidcopolymers (e.g. Eudragit™), maleic anhydride copolymers, copolymersbased on ethylacrylate or methylacrylate, copolymers of acrylic ormethacylic acid esters with quaternary ammonium groups, and the like. Apossible coating is a film of a polymeric gastro-resistant andenterosoluble material, in order to allow activation of thepharmaceutical pellet composition only after it has reached theduodenal-intestinal tract, i.e. more preferably, in order to release theactive ingredient in the duodenal-intestinal tract. Celluloseacetophtalate, cellulose acetopropionate, cellulose trimellitate,hydroxypropyl methylcellulose phthalate, hydroxypropyl methylcelluloseacetate succinate, shellac, acrylic and methacrylic polymers andcopolymers having different molecular weight and solubility depending onpH values may be used for this purpose. In a particular embodiment thecoating is a sustained release coating.

Examples of plasticizers which may be mixed together with the coatingpolymer include, without limitation, polyethyleneglycol, glycerol,phtalate esters, triethylcitrate, etc. In a particular embodiment, thecoat layer does not comprise partially hydrolyzed polyvinyl alcohol.

The thickness of the coating layer used is not critical to the presentinvention. It depends upon the desired release profile of the activeagent and typically is in the micron ranges. In a particular embodiment,a coating level of at least about 10%, more specific at least 15%, andeven more specific at least 20% (w/w) (percentage based on weight of thegranule) is envisaged for sustained release kinetics.

Optionally and before coating, the granules can be covered with a talclayer (optionally together with polysorbate 80).

The granules as described herein, may be used in tablets, capsules,packets and other (compressed) pharmaceutical dosage forms orformulations. These formulations may further optionally containadditives typically used in the formulation of such articles, forinstance flavoring agents (such as anethole, vanillin, ethyl vanillin,and the like), lubricants (such as magnesium stearate), sweeteners (suchas sucrose, mannitol, aspartame, saccharin and its salts), colorantsand/or buffering agents.

The oral dosage form of the present invention is particularly useful forthe controlled, sustained and/or immediate release of one or more activeagents. As used herein, “controlled” or “sustained” release refers tothe release of an active ingredient from a pharmaceutical dosage form ata predetermined rate. “Immediate release” implies that the majority ofthe drug is released from the dosage form upon contact with a biologicalenvironment. For example, in case of an oral dosage form, the majorityof the drug in the dosage form will burst off upon contact with theacidic environment of the stomach. In a particular embodiment of thisinvention, the dosage form as described herein provides an immediaterelease in which the majority, i.e. about 70, 75, 80, 85, 90, 95 or100%, of the active agent(s) is released within the first hour afteradministration of the dosage form or composition comprising it,preferably within the first 50, 40 or 30 minutes, most preferably withinthe first 20 minutes. The release profile can be determined in vitro asdescribed in the present examples, e.g. in USP hydrochloric acid (pH 1)at 37° C. in an USP Apparatus 2.

Also part of the present invention is a method to prepare the granulesas provided herein. A preferred method to prepare spherical granules isby extrusion-spheronization; more in particular by coldextrusion-spheronization. This is the most employed technique as itoffers the advantage to incorporate high amounts of activepharmaceutical ingredient, without producing an excessively largeparticle of drug-loaded granules apart from being more efficient thanthe other techniques for producing granules. Extrusion can be defined asthe process of forcing a material through an orifice or die undercontrolled conditions (cold extrusion generally occurs at (near) roomtemperature, and max. at 50° C.) thus forming cylinders or strandscalled extrudates. During spheronization, these extrudates are brokeninto small cylinders and consequently rounded into spheres (granules;pellets). Hence, extrusion/spheronization is a multiple-step processcapable of making uniformly sized spherical particles referred to aspellets and involving the following sequential steps: (1) dry mixing orblending of ingredients (powders), (2) wet mixing or granulation (i.e.wetting the mix or blend from step (1)), (3) extrusion of the wet massinto extrudates, (4) spheronization of the extrudate, (5) drying of theresulting pellets, and (6) optional coating.

In said process, the active agent(s), partially hydrolyzed PVOH and adiluent, are mixed, wetted (to the extent that is needed to allow thecomposition to be extruded), and granulated in a granulator such as arapid mixer granulator, planetary mixer, fluid bed processer,centrifugal granulator and the like.

In one aspect of the invention, the active agent(s) and other compoundsmay be dissolved, dispersed and/or emulsified in a liquid. Demineralizedwater, ethanol, isopropanol, aceton, and the like, and/or an aqueoussolution of partially hydrolyzed PVOH can be used as granulation liquidor solvent. The moistened mass is extruded through a perforated mesh inorder to produce extrudates (cylindrical filaments). The port of themeshes determines the diameter of the extrudates and in one embodimentis from about 0.2 mm to 3 mm, in particular from about 0.5 mm to about 2mm. The extrusion may be carried out using single screw, double screw,“sieve and basket” kind, “roll extruder”, “ram extruder” extruders orany other pharmaceutically acceptable means to produce extrudates. Theextrudates obtained by extrusion are then spheronized to obtainspherical particles. The spheronization device consists of a hollowcylinder with a horizontal rotating plate. The extrudates are broken inshort segments which are transformed to pellets on the upper surface ofa rotating plate, and in one aspect of the invention at a velocityranging from about 200 rpm to about 2,000 rpm. The pellets may be driedin any pharmaceutically acceptable way, such as drying at roomtemperature and may be accomplished in any apparatus known in the artincluding without limitation, in an oven, a fluidized bed, or amicrowave oven.

The spherical particles are dried and sieved to get the desiredfraction. The dried pellets of desired particle size can optionally befurther coated. Alternatively, the extruded particles are dried andsieved to get the desired fraction. Coating of particles is performed inappropriate coating equipment, e.g., centrifugal coater, coating pan,rotor process, fluid bed coater, and the like.

Other methods of granulation known in the art which involve high shearmay be used to form the pellets including fluid-bed and rotogranulation,centrifugal granulator, or high-shear granulation.

The granules as described herein are preferably formulated for oral orbuccal drug delivery, and in particular, are for oral delivery forrelease of the active agent(s) into the gastro-intestinal tract.Preferably, the granule of the present invention is shaped as orincorporated into (solid) dosage forms for oral administration such asbut not limited to tablets, pills and capsules. In a specificembodiment, the dosage form is a multiparticulate form, meaning that itconsists of a multiplicity of small discrete units (e.g. particles),each exhibiting some desired characteristics. In these systems, thedosage of the drug substance(s) or active ingredient(s) is divided ingranules/particles which typically belong to the multi-particulate drugdelivery forms. Multi-particulates are less dependent on gastricemptying rate, have a lower tendency for local irritation and have areduced risk of dose dumping.

Additional pharmaceutical excipients known in the art may be added tothe dosage form to impart satisfactory processing, disintegration, orother characteristics to the formulation. Such excipients include, butare not limited to, flow enhancers, surfactants, lubricants andglidants, disintegrants, colors, fillers such as lactose, dicalciumdiphosphate, mannitol, starch and derivates, glucose and13-cyclodextrine, pigments, flavors and sweetening agents. Theseexcipients are well known in the art and are limited only bycompatibility and characteristics desired. Examples of useful liquiddiluents are oils, water, alcohols, or mixtures thereof, with or withoutthe addition of pharmaceutically suitable surfactants, suspendingagents, or emulsifying agents. Lubricants and glidants include talc,magnesium stearate, calcium stearate, stearic acid, glyceryl behenate,mineral oil, polyethylene glycol, sodium stearyl fumarate, stearic acid,vegetable oil, zinc stearate, and silicon dioxide. Disintegrantssuitable for the present invention include starches, algins, gums,croscarmelose, crospovidone, sodium starch glycolate, sodium laurylsulfate, microcrystalline cellulose, polacrilin potassium, andmethylcellulose. In a particular embodiment, the dosage form of theinvention comprises a filler.

The terms “drug”, “active agent”, “active ingredient” or“pharmaceutically active ingredient” will be used interchangeablyherein. The (core of the) oral dosage form of the invention typicallycontains one, two, three or more active agents.

The active agent(s) that may be administered using the formulations,systems and methods of the invention are not limited, as the inventionenables the effective delivery of a wide variety of active agents. Theterm “active agent/ingredient or drug” as used herein refers totherapeutic, diagnostic, cosmetic or prophylactic pharmaceutical andveterinary agents as well as other agents. The active ingredient(s) ispresent in at least the core of the granule. The particular nature ofthe active ingredient is not critical, and pharmaceutical andnon-pharmaceutical active ingredients, such as nutritional supplements,detergents, dyes, pesticides, agricultural chemicals, enzymes, and foodsmay also be employed.

The therapeutic or active agent may be selected from any of the variousclasses of such agents including, but not limited to, analgesic agentssuch as acetaminophen, ibuprofen and tramadol, anesthetic agents,anti-anginal agents, antiarthritic agents, anti-arrhythmic agents,antiasthmatic agents, antibacterial agents, anti-BPH agents, anticanceragents, anticholinergic agents, anticoagulants, anticonvulsants,antidepressants, antidiabetic agents such as metformin, antidiarrheals,anti-epileptic agents, antifungal agents, antigout agents,antihelminthic agents, antihistamines, antihypertensive agents,anti-inflammatory agents such as ibuprofen, antimalarial agents,antimigraine agents such as acetaminophen and ibuprofen, antimuscarinicagents, antinauseants, antineoplastic agents, anti-obesity agents,antiosteoporosis agents, antiparkinsonism agents, antiprotozoal agents,antipruritics, antipsychotic agents, antipyretics such as acetaminophenand ibuprofen, antispasmodics, antithyroid agents, antitubercularagents, antiulcer agents, anti-urinary incontinence agents, antiviralagents, anxiolytics, appetite suppressants, attention deficit disorder(ADD) and attention deficit hyperactivity disorder (ADHD) drugs, calciumchannel blockers, cardiac inotropic agents, beta-blockers, centralnervous system stimulants, cognition enhancers, corticosteroids, COX-2inhibitors, decongestants, diuretics e.g. Hydrochlorothiazide (HCT),gastrointestinal agents, genetic materials, histamine receptorantagonists, hormonolytics, hypnotics, hypoglycemic agents,immunosuppressants, keratolytics, leukotriene inhibitors,lipid-regulating agents, macrolides, mitotic inhibitors, musclerelaxants, narcotic antagonists, neuroleptic agents, nicotine,nutritional oils, parasympatholytic agents, sedatives, sex hormones,sympathomimetic agents, tranquilizers, vasodilators, vitamins, andcombinations thereof.

Active agents according to the invention also include nutrients,cosmeceuticals, diagnostic agents, and nutritional agents. Some agents,as will be appreciated by those of ordinary skill in the art, areencompassed by two or more of the aforementioned groups.

Anti-microbial agents such as broad spectrum antibiotics for combatingclinical and sub-clinical infection, for example gentamycin, vancomycineand the like are also appropriate. Other suitable therapeutic agents arenaturally occurring or synthetic organic or inorganic compounds wellknown in the art, including non-steroidal anti-inflammatory drugs,proteins and peptides (that may be produced either by isolation fromnatural sources or through recombination), hormones (for exampleandrogenic, estrogenic and progestational hormones such as oestradiol),bone repair promoters, carbohydrates, antineoplastic agents,antiangiogenic agents, vasoactive agents, anticoagulants,immunomodulators, cytotoxic agents, antiviral agents, antibodies,neurotransmitters, oligonucleotides, lipids, plasmids, DNA and the like.

Suitable therapeutically active proteins include e.g. fibroblast growthfactors, epidermal growth factors, platelet-derived growth factors,macrophage-derived growth factors such as granulocyte macrophage colonystimulating factors, ciliary neurotrophic factors, tissue plasminogenactivator, B cell stimulating factors, cartilage induction factor,differentiating factors, growth hormone releasing factors, human growthhormone, hepatocyte growth factors, immunoglobulins, insulin-like growthfactors, interleukins, cytokines, interferons, tumor necrosis factors,nerve growth factors, endothelial growth factors, osteogenic factorextract, T cell growth factors, tumor growth inhibitors, enzymes and thelike, as well as fragments thereof.

As evident for a person skilled in the art, the load of the activeagent(s) comprised in the pharmaceutical dosage form according to thisinvention, may vary depending on the active agent(s) used, and theenvisaged application area. In general, the granule, in particular thecore thereof, of the invention may comprise about and between 40-95wt. %of active agent. In a specific embodiment the granule may comprise aboutand between 50-90wt. % of active agent, or about and between 50-80wt. %of active agent, and may comprise preferably at least or about 40%, morepreferably at least 45 wt. %, 50 wt. %, 55 wt. %, 60 wt. %, 65 wt. %, 70wt. %, 80 wt. % or more wt. % of the active agent, including all valuesin between. As mentioned herein, any % is weight-by-weight, relative tothe total weight of the granule core, or optionally the formulation. Asis evidenced by the present examples, the dosage form of the presentinvention is surprisingly useful for high drug loading, i.e. a drugloading of more than 50 wt. % can be obtained without any disadvantages.In a particular embodiment, the invention encompasses a granulecomprising at least 50 wt. % of an active agent in the core, and evenmore particular at least 60 wt. %, 70 wt. %, 80 wt. % or even 90 wt. %of an active agent or combination of two or more active agents.

The drug release rate is tested during drug dissolution tests as e.g.described in the present examples.

The granules according to this invention may be in any suitableadministration form. For example, a multiplicity of the granules may becompressed during a tableting process providing a tablet or any othercompressed dosage form. Alternatively, the granules may be encapsulated.A further example is a sachet, a unit dose comprising a multiplicity ofthe granules as provided herein. Preferably the composition comprisingthe granules of the present invention is an oral dosage form.

In a further embodiment, the present invention encompasses apharmaceutical composition comprising a dosage form as described hereinand a pharmaceutically acceptable carrier, excipient and/or diluent,known to the skilled person.

In a further aspect, the present invention provides a dosage form orcomposition as defined herein for use as a medicament, in particular forthe controlled, sustained and/or immediate release of one or more activeagents.

Furthermore, the present invention provides a method for the immediateor controlled release of one or more active agents; said methodcomprising administering to a patient in need thereof a solidpharmaceutical dosage form as defined herein.

The present invention also provides a method of preparing a dosage form,in particular a granule; said method comprising the steps of:

mixing an active agent, partially hydrolyzed polyvinyl alcohol and adiluent, in particular MCC,

adding a liquid such as e.g. water;

extruding the wetted mixture to obtain an extrudate,

spheronizing of the extrudate to obtain a plurality of granules, and

drying the plurality of granules.

In case a partially hydrolyzed PVOH solution (e.g. dissolved PVOH indemineralized water) is used in the process, no additional wet massingliquid is needed.

In a further embodiment the method comprises the addition of a coatlayer.

In addition, the present invention provides a granule obtainable by aprocess as defined herein.

This invention will be better understood by reference to the Examplesthat follow, but those skilled in the art will readily appreciate thatthese are only illustrative of the invention as described more fully inthe claims that follow thereafter. Particular embodiments and examplesare not in any way intended to limit the scope of the invention asclaimed. Additionally, throughout this application, various publicationsare cited. The disclosure of these publications is hereby incorporatedby reference into this application to describe more fully the state ofthe art to which this invention pertains.

EXAMPLES

In the first part of this study, PVOH was evaluated as pelletisation aidin high drug-loaded pellets produced by extrusion/spheronisation,whereby pellet properties (i.e. aspect ratio, sphericity, particle sizedistribution . . . ) were compared with MCC pellets as a reference. Inthe second part of this study, the use of those pellets in fixed dosecombination therapy was investigated with an acetaminophen/tramadol.HClformulation by which pellet quality and drug release was evaluated.Furthermore, the use of a coat and a taste masking agent was evaluated,as well as the in vivo release characteristics of the pellets.

1. MATERIALS AND METHODS 1.1 Materials

A pharmaceutical grade PVOH 4-88 (88% hydrolysed), obtained from Merck(Darmstadt, Germany), and microcrystalline cellulose (Avicel® PH101)(FMC Wallingstown, Little Island, Cork, Ireland) were used aspelletisation aids. Micronized acetaminophen (Atabay, Istanbul, Turkey),tramadol.HCl (Proto Chemicals AG, Mitlodi, Switzerland), andmetformin.HCL (Granules, Jeedimetla, India) were used as model drugs.Demineralised water or an aqueous solution of PVOH were used asgranulation liquid.

For coating trials, a methacrylic acid copolymer (Eudragit™ NM 30D) andhydroxypropylmethylcellulose (Methocel™ E5) were supplied by Evonik(Darmstadt, Germany) and The Dow Chemical Company (Midland, Mich., USA),respectively. Talc and polysorbate 80 (Tween 80™) were obtained fromFagron (Waregem, Belgium).

A more detailed description of the particle size and geometry of theused raw materials is listed in Table 1.

TABLE 1 Powder characteristics of raw materials D10 D50 D90* Aspect (μm)(μm) (μm) ratio Sphericity Acetaminophen 1.7 6.4 20.1 0.58 0.84Metformin•HCl 8.4 51.6 150.2 0.66 0.87 MCC 19.8 54.1 113.1 0.53 0.76*D90 means that 90% of the particles have a size of less than thespecified diameter.

1.2 Plasticity Measurements: Atterberg Limits

An ASTM standard test (ASTM D 4318) was used to quantify the liquidlimit, plastic limit and plasticity index of the wet mass. Theplasticity index was defined as the range of water content over which awet mass behaves plastically. Mathematically, it was calculated as thedifference between the liquid limit and the plastic limit. The liquidlimit was determined by spreading an amount of the wet mass in a brasscup. A grooving tool was then used to divide the material into twosymmetrical halves separated by 13 mm. By repeatedly dropping the cup ina mechanical device, both halves were able to flow towards the centre ofthe cup and make contact at the bottom of the groove. As the multipointliquid limit (i.e. method A of ASTM D 4318) was used, four trials over awide range of water contents were performed. The number of dropsrequired before both halves made contact with each other was plotted asa function of water content on a semi-logarithmic graph, with the watercontent as ordinates on the arithmetical scale, and the number of dropsas abscissas on a logarithmic scale. Subsequently, the best fit line wasplotted. The water content corresponding to the intersection of the linewith the 25-drop abscissa was taken as the liquid limit of the wet mass.To determine the water content from each trial, a standard ASTM test(ASTM D 2216) was used. Therefore, initial masses (container plus wetmass) were recorded immediately and after 24 h oven drying at 105° C.The plastic limit was determined by alternately pressing and rolling asmall amount (±12 g) of wet masses with different water content into a3.2 mm diameter thread. The water content at which the thread crumbledand could no longer be pressed together and re-rolled was reported asthe plastic limit. All experiments were performed in triplicate.

1.3 Production of Pellets

The active pharmaceutical ingredient (API), PVOH and Avicel® PH101 orAPI and Avicel® PH101 (batch size: 200 g) in different ratios were mixedduring 5 min. in a planetary mixer (Kenwood Chief, Hampshire, UK), usinga K-shaped mixing arm (Table 2). Demineralized water or a PVOH aqueoussolution (prepared by dissolving PVOH in demineralized water at 80° C.and cooled down to room temperature prior to addition) was graduallyadded to the powder mixture, while mixing was continued during 10 min.The wet mass was extruded at an extrusion speed of 100 rpm using asingle screw extruder (Dome extruder DG-L1, Fuji Paudal, Tokyo, Japan)equipped with a dome shaped extrusion screen with 1.0 mm perforations.The resulting extrudates were spheronised for 1 min. at a speed of 1000rpm using a spheroniser having a cross-hatched geometry friction plate(Caleva Model 15, Caleva, Sturminster Newton, Dorset, UK). The pelletswere oven dried for 24 h at 40° C. Each batch of pellets was sieved for5 min. at 2 mm amplitude using a sieve shaker (Retsch, Haan, Germany) toobtain the 0.710-1.00 mm size fraction.

TABLE 2 Composition of pellet formulations Water Concentration (%) Ratiocontent Formulation Acetaminophen PVOH MCC (PVOH_(/)MCC) (%)* 1 70 0 30 0/100 — 2 70 1.5 28.5  5/95 53.3 3 70 3 27 10/90 46.2 4 70 6 24 20/8038.3 5 70 15 15 50/50 — 6 80 0 20  0/100 — 7 80 1 19  5/95 43.3 8 80 218 10/90 40.6 9 80 4 16 20/80 33.2 10 80 10 10 50/50 22.9 11 90 0 10 0/100 — 12 90 0.5 9.5  5/95 36.3 13 90 1 9 10/90 35.0 14 90 2 8 20/8030.2 15 90 5 5 50/50 24.5 16 — — 100 — 120   17 50 — 50 — 55.7 WaterRatio content Form. Metformin•HCl PVOH MCC (PVOH/MCC) (%)* F18 90 0 10 0/100 — F19 88.7 1.5 9.8 13/87 18.5 F20 87.3 2.9 9.7 23/77 17.0 *Watercontent was calculated as a percentage of the total dry weight of eachformulation

1.4 Evaluation of Different PVOH Grades

Acetaminophen and Avicel® PH101 (with or without the addition ofdifferent PVOH grades, Table 3) were dry mixed in different ratiosduring 5 min in a planetary mixer (Kenwood Chief, Hampshire, UK), usinga K-shaped mixing arm. The aqueous PVA solution was gradually added tothe powder mixture. After 10 min of mixing, the wet mass was extruded atan extrusion speed of 100 rpm using a single screw extruder (Domeextruder DG-L1, Fuji Paudal, Tokyo, Japan) equipped with a dome-shapedextrusion screen having a thickness of 1.2 mm and 33 1 mm-perforationsper cm². The resulting extrudates were spheronized for 1 min at a speedof 1000 rpm using a spheroniser having a cross-hatched geometry frictionplate (Caleva Model 15, Caleva, Sturminster Newton, Dorset, UK) with adiameter of 38 cm. The features on the friction plate had a size of 6.5mm and were positioned at a distance of 3.5 mm of each other.

TABLE 3 Composition of the pellet formulations. For each formulationF1-F5 resp., all experiments were conducted using different PVOH grades(i.e. PVA505, 4-88, 5-88, 8-88, 16-88, 26-88 and 40-88). WaterConcentration (%) Ratio content Form. Acetaminophen PVOH MCC (PVOH/MCC)(%)* F1 90 0 10  0/100 — F2 90 0.5 9.5  5/95 36.3 F3 90 1 9 10/90 35.0F4 90 2 8 20/80 30.2 F5 90 5 5 50/50 24.5 *Water content was calculatedas a percentage of the total dry weight of each formulation

1.5 Preparation of Sustained Release Pellets by Coating

The coating suspension (batch size 1 kg) was prepared in four steps: (1)10 g of HPMC was added to 559.7 g demineralized water. Subsequently, themixture was heated to 55° C. and mixed using a high speed mixer(Silverson™ L4R, Silverson Machines, Waterside, Chesham, Bucks, England)until a clear solution was obtained; (2) 30.3 g of a 33% aqueoussolution of polysorbate 80 and 100 g talc were added and dispersed forat least 10 min; (3) the resulting excipient suspension was slowlypoured into 300 g Eudragit™ NM 30D with a magnetic stirrer at roomtemperature for 5 min; (4) the spray suspension was passed through a 0.5mm sieve and was then continuously stirred with a magnetic stirrer atroom temperature during coating experiments.

Varying coating levels (0, 8, 14 and 20%, w/w) were applied to pelletscontaining 87.3% (w/w) metformin.HCl (F20 in Table 2, sieve fraction850-1120 μm). All experiments were performed using a laboratory scalefluid bed granulator (GPCG 1, Glatt, Binzen, Germany). The spraysuspension was added at a flow rate of 1.85 mL/min through a 0.8 mmnozzle (bottom spray). The atomizing pressure and inlet air temperaturewere set at 2 bar and 40° C., respectively. The resulting outlet airtemperature and product temperature were between 20 and 25° C. An inletair velocity of 5 m/s was used and the filter bags were shaken every 15s for a period of 5 s. All coated pellets were cured in an oven at 40°C. for 24 h. An overview of their final composition is listed in Table4.

Composition of coated metformin•HCl pellet formulations. Concentration(%) Form. Metformin•HCl PVOH MCC Coating F21 87.3 2.9 9.7 0.0 F22 80.42.7 8.9 7.9 F23 74.9 2.5 8.3 14.2 F24 69.5 2.3 7.7 20.4

1.6 Taste Masking

Usually, the drug load of taste masked pellets is limited as largeamounts of MCC (to enable extrusion-spheronisation) and taste maskingpolymer are needed. As the MCC concentration could be lowered by theaddition of PVA, it was the aim to develop high drug loaded taste maskedibuprofen pellets.

Ibuprofen and Avicel® PH101 (with or without the addition of differentPVA concentrations, Table 5a) were dry mixed in different ratios during5 min in a planetary mixer (Kenwood Chief, Hampshire, UK), using aK-shaped mixing arm. The aqueous PVA solution was gradually added to thepowder mixture. After 10 min of mixing, the wet mass was extruded at anextrusion speed of 100 rpm using a single screw extruder (Dome extruderDG-L1, Fuji Paudal, Tokyo, Japan) equipped with a dome-shaped extrusionscreen having a thickness of 1.2 mm and 33 1 mm-perforations per cm2.The resulting extrudates were spheronized for 1 min at a speed of 1000rpm using a spheroniser having a cross-hatched geometry friction plate(Caleva Model 15, Caleva, Sturminster Newton, Dorset, UK) with adiameter of 38 cm. The features on the friction plate had a size of 6.5mm and were positioned at a distance of 3.5 mm of each other.

TABLE 5a Composition of the pellet formulations. All experiments wereconducted using PVA4-88. Water Concentration (%) Ratio content Form.Ibuprofen PVA MCC (PVA/MCC) (%)* F1 80 0 20  0/100 — F2 80 1 19  5/9543.3 F3 80 2 18 10/90 40.6 F4 80 4 16 20/80 33.2 *Water content wascalculated as a percentage of the total dry weight of each formulation

Formulations with different PVA content were processed. The PVA/MCCratios tested at a constant drug load of 80% (w/w). Whereas highdrug-loaded formulations without the addition of PVA (i.e. F1 in Table5a) could not be processed via extrusion-spheronisation due to sharkskinning and the high brittleness of the extrudates duringspheronisation, the addition of a low PVA concentration improved theextrusion properties of the formulations, yielding extrudates with asmooth surface, even for formulations with a low MCC content (e.g. F3containing 80% ibuprofen, 2% PVOH and only 18% MCC).

Based on its high drug content and low friability (0.54±0.12%),formulation 3 (F3) was selected as starting material for coating trials.

TABLE 5b Composition of coated ibuprofen pellet formulations.Concentration (%) Form. Ibuprofen PVA MCC Coating F5 67.6 2.3 16.9 13.2

1.7 Characterization 1.7.1 Pellet Shape and Size

The size and shape of the pellets were determined using dynamic imageanalysis (QicPic, Clausthal-Zellerfeld, Germany). D₁₀, D₅₀ and D₉₀,which are the respective particle sizes at 10, 50 and 90% cumulativeundersize, were determined (Kooiman et al., 2009). Furthermore, thewidth of the particle size distributions (PSD) was determined bycalculating the span, as follows:

Span (μm)=D ₉₀ −D ₁₀

An independent sample t-test was performed with SPSS Statistics 23 (IBM,New York, United States) to detect significant differences in spanbetween formulations. The shape of the pellets was expressed as aspectratio (AR) and sphericity. AR was defined as the ratio of the maximaland minimal Feret diameter (Feret_(max) and Feret_(min), respectively).

${AR} = \frac{Feret_{\max}}{Feret_{\min}}$

Sphericity was defined as the ratio between the perimeter of a circlethat has the same projected area (A) as the particle (P_(EQPC)) to themeasured perimeter (P_(REAL)), and is thus a value between 0 and 1 (Yuand Hancock, 2008).

${Sphericity} = {\frac{P_{EQPC}}{P_{REAL}} = \frac{2\sqrt{\pi A}}{P_{REAL}}}$

The measurements were performed in triplicate (±10 g for each sample).

1.7.2 Loss on Drying (LOD)

After drying, the residual moisture content of the pellets was analysedby loss on drying (LOD) using a Mettler LP16 moisture analyser,including an infrared dryer and a Mettler PM460 balance (Mettler-Toledo,Zaventem, Belgium). A sample of approximately 2 g was dried at 105° C.until the rate of change was less than 0.1% LOD for 30 s and the % LODwas then recorded. The measurements were performed in triplicate.

1.7.3 Friability

Pellet friability was determined using a friabilator equipped with anabrasion drum (Pharma Test, Hainburg, Germany). Approximately 10 g ofpellets within the size range of 0.710 to 1.00 mm were accuratelyweighed and added to the abrasion drum together with 200 glass beads (4mm in diameter). The friabilator was set at 25 rpm during 10 min. At theend of the run, the content of the abrasion drum was sieved onto a sieveof 0.5 mm or 850 μm and the fraction below 0.5 mm or 850 μm wasaccurately weighed. Friability was measured in triplicate and calculatedas follows:

$\mspace{79mu} {{{Friability}(\%)} = {\frac{{Fraction} < {0.5\mspace{14mu} {{mm}(g)}}}{{Total}\mspace{14mu} {sample}\mspace{14mu} (g)} \times 100}}$     or${{Friability}\mspace{20mu} \%} = {{{Fraction} < {850\mspace{14mu} \mu \; {m(g)}{{Friability}(\%)}}} = {\frac{{Fraction} < {850_{11}{m(g)}}}{{Total}\mspace{14mu} {sample}\mspace{14mu} (g)} \times 100}}$

1.7.4 Image Analysis

Photomicrographs of pellets were taken with a digital camera (Camedia®C-3030 Zoom, Olympus, Tokyo, Japan), linked with a stereomicroscopesystem (SZX9 DF PL 1.5×, Olympus, Tokyo, Japan). A cold light source(Highlight 2100, Olympus, Germany) and a ring light guide (LG-R66,Olympus, Germany) were used to obtain top light illumination of thepellets against a dark surface.

Scanning electron microscopy (SEM) was used to determine differences inpellet surface morphology. Prior to imaging, samples were coated with athin gold layer. SEM images were recorded using a tabletop SEM (PHENOM™,FEI Company).

1.8 IN VITRO DISSOLUTION

Drug release from pellets was determined using USP apparatus 2(paddles), in a VK 7010 dissolution system combined with VK 8000automatic sampling station (Vankel Industries, New Jersey, USA). Theamount of pellets corresponding to 500 mg acetaminophen or 325 mgacetaminophen and 37.5 mg tramadol.HCl were placed in 0.1 N HCl pH 1(900 ml, at a temperature of 37±0.5° C.), while the rotational speed ofthe paddles was 100 rpm. Samples of 5 ml were withdrawn at 10, 20, 30,40, 50, 60, 70, 80, 100 and 120 min. (without medium replacement) andspectrophotometrically analyzed for acetaminophen concentration at 244nm by means of a Shimadzu UV-1650PC UV-VIS double beam spectrophotometer(Antwerpen, Belgium). The acetaminophen content in the samples wasdetermined by linear regression using a calibration curve between 1.5and 15 μg/ml. Tramadol.HCl was analyzed via ‘high performance liquidchromatography’ (HPLC). The HPLC system (Merck-Hitachi D-7000, Tokyo,Japan) consisted of a pump (Merck-Hitachi L-7200), an autosampler(Merck-Hitachi L-7250), a LichroSpher 100 RP-8 column (4.6×150 mm, 5 μm)(Merck Millipore, Darmstadt, Germany), and an UV-detector (Merck-HitachiL-7400) set at 272 nm. For the preparation of the mobile phase, 0.05 Mmonobasic potassium phosphate was mixed with acetonitrile (Biosolve,Valkenswaard, the Netherlands) in a ratio 4:1 (vol/vol). The analyseswere performed at 25° C., and the flow rate was set at 1 ml/min. Avolume of 25 μL was injected onto the HPLC system. Each formulation wasevaluated in triplicate.

Drug release from (un)coated metformin hydrochloride pellets wasdetermined using the paddle method on a VK 7010 dissolution system(VanKel Industries, New Jersey, USA) at a speed of 100 rpm. An amount ofpellets corresponding to 250 mg metformin.HCl was placed in 900 mL 0.1 NHCl (pH 1.2) or phosphate buffer solution (pH 6.8), set at a temperatureof 37±0.5° C. Samples were withdrawn at 0.5, 1, 2, 4, 6, 8, 12, 16, 20and 24 h, and spectrophotometrically (UV-1650PC, Shimadzu Benelux,Antwerp, Belgium) analysed using a wavelength of 232 nm.

1.9 IN VIVO

The bioavailability study (application ECD 2013/127) was approved by theEthical Committee of the Faculty of Veterinary Medicine (GhentUniversity).

1.9.1 Animal Study

In vivo experiments were performed using a sustained release pelletformulation described above (i.e. F24) and a reference formulation(Glucophage™ SR 500 mg, ½ tablet). Open label cross-over assays wereperformed on 6 male beagle dogs (10-13 kg) with a wash-out period of atleast 8 days. The pellet and reference formulations were orallyadministered to fasted dogs (no food intake was allowed 12 h prior todrug administration) with 20 mL water. During the experiment the dogswere only allowed to drink water. Blood samples were collected after 1,2, 3, 4, 5, 6, 8 and 12 h post administration, and were stored at −25°C. until analysis.

1.9.2 Metformin Assay

An extraction method developed by Gabr et al., 2010, was optimized.After de-freezing, plasma samples were centrifuged using a Centric 322A(Tehtnica, Slovenia) at 2300 g for 10 min. 280 μL of the supernatant wasspiked with 20 μL 0.05 mg/mL ranitidine solution. During a firstextraction step, 50 μL 10 M sodium hydroxide solution and 3 mL organicphase (1-butanol/hexane, 50/50, v/v) were added. The tubes were mixedusing a Turbula™ mixer (Willy A. Bachofen Maschinenfabrik, Switzerland)for 30 min at an intensity of 79 rpm. After centrifugation the upperorganic layer was transferred to a clean test tube. Back extraction wasperformed by adding 1 mL 2M HCl, mixing the tubes (79 rpm, 10 min) andcentrifugation (10 min, 2300 g). Afterwards the organic layer wasremoved, and 400 μL sodium hydroxide (10 M) and 2 mL organic phase(1-butanol/hexane, 50/50, v/v) were added. After mixing (79 rpm, 30 min)and centrifugation (10 min, 2300 g) the organic layer was transferredinto a clean glass tube and evaporated to dryness under a nitrogenstream.

The HPLC system (Merck-Hitachi, Darmstadt, Germany) consisted of anisocratic solvent pump (L-7100) set at a constant flow rate of 0.7mL/min, an auto-sampler injection system (L-7200) with a 100 μL loop(Valco Instruments Corporation, Houston, Tex., USA), a reversed-phasecolumn and pre-column (LiChroCart® 250-4 and LiChrospher® 100RP-18 5 μm,respectively) and a variable wavelength UV-detector (L-7400) set at 236nm. The mobile phase composition remained constant over time andconsisted of potassium dihydrogen phosphate buffer (adjusted to pH 6.5with 2 M NaOH)/acetonitrile (66/34, v/v) and 3 mM sodium dodecylsulphate (SDS).

1.9.3 Data Analysis

Peak integration was performed using the software package D-7000 HSMChromatography Data Manager. The peak plasma concentration (C_(max)),time to reach C_(max) (T_(max)), half value duration (HVD_(t50%Cmax))and area under the curve (AUC_(0-12h)) were calculated using acommercial software package (MATLAB 8.6, The MathWorks, Natick, USA,2015). The sustained-release characteristics of the formulation wereevaluated by calculating the R_(D) ratio between the HVD_(t50%Cmax)values of a test formulation and an immediate-release formulation. Aratio of 1.5, 2 and >3 indicates low, intermediate and strong sustainedrelease characteristics, respectively. A HVD_(T50%Cmax) value of 3.2 hfor immediate release metformin tablets, administrated to beagle dogs,was abstracted from literature and used to calculate the R_(D) ratio.(Meier et al. 1974; Gabrielsson et al. 2000; Lalloo et al. 2012).

1.9.4 Statistical Analysis

The effect of metformin.HCl formulation on the bioavailability wasassessed using an independent sample t-test. The normality of theresiduals was evaluated with a Kolmogorov-Smirnov test. To test theassumption of variance homogeneity, a Levene's test was used. Thestatistical analysis was performed using SPSS (IBM SPSS Statistics forWindows, version 23.0, Armonk, N.Y., USA, 2015).

2. RESULTS AND DISCUSSION 2.1 Evaluation of PVOH as Pelletisation Aidfor the Production of Acetaminophen Pellets

Pellets with acceptable quality containing only acetaminophen and MCCcould be processed with a maximum drug concentration of 50% and a watercontent of 55.6% (F17). O'Connor et al. similarly observed that MCC(Avicel PH-101) did not yield acceptable pellets at higher drugconcentration (Oconnor and Schwartz, 1985). In this study PVOH wasevaluated as pelletisation aid, in order to raise drug concentrationinside the pellets. However, preliminary studies have shown that aminimal MCC concentration (5%) was required to overcome problems relatedto the tackiness effect of PVOH during extrusion, and to improve watertolerance of the formulation (Mallipeddi et al., 2010). MCC acts like a‘molecular sponge’, which is able to absorb and retain large quantitiesof water due to its large surface area and high internal porosity, andtherefore hold water when pressure was applied during extrusion (Fieldenet al., 1988).

Fifteen formulations were processed, whereby acetaminophen concentrationranged from 70% to 90% and the ratio PVOH/MCC ranged from 0/100 to 50/50(Table 2). The formulations without PVOH could not be spheronised, asthe extrudates were to brittle and broke up inside the spheroniser (F1,F6 and F11). Formulation 5, containing 15% PVOH and acetaminophen asactive ingredient, was not processable as the extrudates stickedtogether after exiting the extruder.

Lower water content was required for formulations containing higheracetaminophen concentration and PVOH/MCC ratio, mainly due to adecreased MCC concentration, because MCC has a large water-holdingcapacity (Chatlapalli and Rohera, 1998) (Verheyen et al., 2009).Additionally, Law et al. studied the use of hydrophilic polymers withMCC to improve extrusion/spheronisation, and indicated that moreadhesive polymers required lower levels of water, as over-hydrationcaused agglomeration (Law and Deasy, 1998). Therefore, formulationscontaining an increased PVOH concentration, required a reduced watercontent.

Pellets were prepared with PVOH added as a dry powder or predissolved inwater. Three formulations were processed via the dry addition method(i.e. F10, F12 and F13). After drying, the residual moisture content wasbelow 1.5% for all formulations.

The particle size distributions (PSD) of different formulations werecompared with reference pellets made of pure MCC pellets (F16) (FIG. 1).

The pellet size of formulations containing PVOH was higher compared tothe reference. J. Chatchawalsaisin et al. reported that pelletdimensions depended on extrudate diameter and length to which theextrudate was chopped (Chatchawalsaisin et al., 2005). During extrusion,it was noticed that extrudates containing PVOH were longer compared toMCC extrudates. Therefore, PVOH extrudates broke into longer segmentsduring spheronisation and provide bigger pellets accordingly.Additionally, pellet size could also increase due to mass transferbetween pellet particles. M. Koester et al. reported that besidesplastic deformation, mass transfer must be considered duringspheronisation (Koester and Thommes, 2010). Microscopic images showedagglomeration of smaller particles on the surface of the pellets (datanot shown), which could consolidate with the larger pellets duringspheronisation (plastic deformation), leading to a higher particle size.

Pellets developed for pharmaceutical applications, are required to havea narrow PSD (Dukic-Ott et al., 2009). Therefore, the span, whichindicates the width of the PSD was determined and reported in Table 6. Asmall span corresponds with a narrow PSD.

TABLE 6 Span (d₉₀-d₁₀, μm) (mean ± standard deviation, n = 3) offormulations as a function of drug concentration (70-90%), PVOH/MCCratio (0/100-50/50). PVOH was added either as dry powder or aqueousdispersion. The significance of the results was determined withindependent sample t-test. Span values in the same row with differentsuperscripts are different at the 0.05 level of significance. PVOHmethod addition Formulation Dry Wet 70% F2 1486 ± 348^(a) 640 ± 23^(b)F3 1040 ± 85^(a)  679 ± 52^(b) F4 1158 ± 197^(a) 467 ± 32^(b) 80% F71198 ± 181^(a) 1114 ± 64^(a)  F8 926 ± 42^(a) 998 ± 35^(a) F9 965 ±68^(a) 803 ± 22^(b) 90% F14 1143 ± 198^(a) 1172 ± 355^(a) F15 2338 ±253^(a) 805 ± 73^(b) Ref. MCC 434 ± 19 

An independent sample t-test was used to detect significant differencesin span between formulations either processed with PVOH in dry powderform or solution. In general, the use of PVOH solution caused asignificant (P<0.05) decrease in span, possibly due to the fact thatPVOH solution, which act as a liquid binder, was more homogenouslydistributed during granulation. R. Chatlapalli also reported that theuse of a liquid binder (i.e. hydroxypropyl cellulose in isopropylalcohol) was more effective than in dry powder form (Chatlapalli andRohera, 1998). If PVOH/MCC ratio was raised, a narrower PSD wasobtained. F4 combined with the wet addition method for PVOH resulted inthe lowest span (467±32 μm) and did not show significant difference(p>0.05) with the reference MCC pellets. However, it was noticed thatincreasing the drug load from 70% to 90% and thereby decreasing theamount of PVOH and MCC in the pellets, had a negative influence on thespan. This indicates that PVOH and MCC were required to providesufficient rigidity, plasticity and water absorbing capacity to allowproduction of spheres with narrow PSD (Wlosnewski et al., 2010).Overall, the span values of formulations containing PVOH were higher,and thus PSD broader.

Using a standard test for measuring the plasticity index of soil (i.e.the Atterberg method, ASTM D 4318) the impact of PVOH addition on theplasticity of the wet mass was determined. Whereas an increase of drugcontent in MCC formulations was correlated with a drop of the plasticityindex (20.7 for a 50/50 API/MCC mixture vs. 4.8 and 8.9 for formulationscontaining 80% paracetamol and 90% metformin, respectively), theaddition of PVOH significantly improved the plasticity of the wet masswhich is an important factor during an extrusion-spheronisation process(Table 7).

TABLE 7 Plasticity indexes (mean ± SD, n = 3) of the wet mass used forthe manufacturing of different pellet formulations. Concentration (%)Plasticity Form. Acetaminophen PVOH MCC index (%) F6 80 0 20  4.8 ± 1.3F7 80 1 19  4.9 ± 0.4 F8 80 2 18 12.3 ± 3.0 F9 80 4 16 16.5 ± 0.1 F10 8010 10 48.5 ± 1.3 F17 50 — 50 20.7 ± 3.0 Plasticity Form. Metformin•HClPVOH MCC index (%) F18 90 0 10  8.9 ± 1.8 F20 87.3 3 9.7 17.9 ± 0.9

A plasticity index of the wet mass about and between 5% and 30%, inparticular between 10% and 20%, and more in particular between 12% and20% resulted in enhanced extrusion spheronization properties, even athigh drug load.

The pellet morphology was measured in terms of AR and sphericity,whereby the fraction 710-1000 μm of MCC-pellets was compared with PVOHformulations after drying (FIG. 2). A mean AR lower or equal to 1.20 wasconsidered as sufficient for pharmaceutical pellets (Krause et al.,2009).

Wet addition of PVOH solution resulted in a lower AR. However, it shouldbe considered that PVOH formulations have a wider range of AR comparedto MCC pellets. Therefore, due to the wider range of AR, it was hard todistinguish any influence of drug load or addition of PVOH as dry powderform/solution. Sphericity was less sensitive to detect any differencesbetween formulations. However, all formulations had a high sphericity(>0.85). It's notable that F4, with narrow PSD, complies with a meanAR≤1.2 and sphericity >0.9. SEM photographs were used to determinedifferences in pellet surface morphology (data not shown). In agreementwith AR and sphericity, a smooth contour and surface can be observed onthese photographs.

The friability (Table 8) was measured in order to determine themechanical properties of the pellets. Pellets are required to withstandmechanical stress for post-processing steps (e.g. coating, packaging)which could occur for example during coating of pellets.

TABLE 8 Friability (%)(mean ± standard deviation, n = 3 of pellets(710-1.00 mm) as a function of drug load and PVOH/MCC ratio. Friability% PVOH dry PVOH solution 70% F2 0.10 ± 0.02 0.15 ± 0.01 DRUG F3 0.39 ±0.01 0.35 ± 0.02 F4 0.18 ± 0.02 0.02 ± 0.01 80% F7 0.41 ± 0.01 0.66 ±0.03 DRUG F8 1.12 ± 0.03 0.85 ± 0.04 F9 1.50 ± 0.04 0.55 ± 0.01 F10 0.40± 0.02 — 90% F12 1.35 ± 0.16 — DRUG F13 1.36 ± 0.23 — F14 3.90 ± 0.200.35 ± 0.01 F15 0.56 ± 0.07 0.17 ± 0.01

The friability was slightly higher for pellets with a higher drug load,possibly due to the lower amount of excipients (i.e. PVOH and MCC),which contribute to the mechanical strength of pellets. Furthermore, wetaddition of at least 2% PVOH resulted in a lower friability. Inliterature, different values for friability of pellets, ranging between1.2 and 3.07%, have been reported (Gazzaniga et al., 1998; Vertommen andKinget, 1997). All pellets processed with PVOH solution have afriability below 1% for all drug loadings (70-90%), whereby F4 has thelowest friability (0.02±0.01%).

The in vitro dissolution profiles of pellets with different drug load(70-90%) processed with PVOH in dry powder form or solution werecompared with MCC pellets (F17) containing a drug load of 50%acetaminophen (FIG. 3). Drug release was mainly dependent on theconcentration acetaminophen inside the pellets. Acetaminophen wascompletely released after 30, 20 and 10 min for pellets containing 70,80 or 90% acetaminophen, respectively. It is known that MCC pellets donot disintegrate, and therefore release the drug by diffusion (Kranz etal., 2009). However, pellets containing higher drug load were able todisintegrate and thereby release the drug faster. Furthermore, drugrelease was independent of PVOH addition method, since no difference wasobserved between formulation containing PVOH as dry powder form andformulations containing PVOH solution.

All tested PVOH grades (Table 3) could enhance theextrusion-spheronisation properties of the wet mass. Despite, morestickiness to the friction plate was observed in case higher molecularweights were used. This phenomenon was not observed when lower molecularweight PVOH grades (e.g. PVA505, PVA4-88, PVA5-88 and PVA18-88) wereused. Stickiness to the friction plate could be partially countered byadding less water. Although, more shark skinning and extrudatebrittleness was found in case less water was added.

Especially partially (including low) hydrolysed PVOH grades areinteresting extrusion-spheronisation aids because of their high aqueoussolubility. Based on their high solubility in water, they can be easilyadded via the wet addition method. All low and partially hydrolysed PVOHgrades could enhance the extrusion-spheronisation properties of the wetmass. The range of water concentration was found more narrow withincreasing PVOH molecular weight.

2.2 Evaluation of PVOH as Pelletisation Aid for the Production of FixedDose Combination (Acetaminophen/Tramadol.HCl)

In the second part of this study, the use of pellets with PVOH aspelletisation aid in fixed dose combinations was evaluated. Fixed dosecombinations consist out of 2 or more drugs that are combined inside thepellet and thus requires pellets which could contain a high drugconcentration. F4, which contains 70% acetaminophen, 6% PVOH and 24%MCC, was the most promising formulation with a narrow PSD (low spanindex), mean AR≤1.2, sphericity >0.9 and friability <1%. Thisformulation was transformed to a fixed dose combination ofacetaminophen/tramadol.HCl (325/37.5) (Table 9).

TABLE 9 Composition of pellet formulation containing acetaminophen andacetaminophen/tramadol. Acetaminophen/ Concentration (%) AcetaminophenTramadol•HCl Acetaminophen 70 62.8 Tramadol•HCl — 7.2 PVOH 6 6 MCC 24 24Water content (%)* 38.3 35 *Water content was calculated as a percentageof the total dry weight of each formulation

The optimal water content of formulations containingacetaminophen/tramadol.HCl was slightly lower compared to acetaminophenformulation, since the aqueous solubility of tramadol (30-100 mg/ml)(Sudha et al., 2010) was higher compared to acetaminophen (14.3 mg/ml)(Kalantzi et al., 2006). This confirms that drug solubility influencesthe required amount of water for the production of pellets (Verheyen etal., 2009). The span of formulations containing acetaminophen andacetaminophen/tramadol.HCl were compared with reference pellets withoutacetaminophen (F16) (Table 10).

TABLE 10 Particle size data (D₁₀, D₅₀, D₉₀ and span) (mean ± standarddeviation, n = 3) of formulations containing acetaminophen oracetaminophen/tramadol•HC1 (62.8/7.2). MCC pellets were used asreference. The significance of the results between formulations wasdetermined with an independent sample t-test. Span values) withdifferent superscripts are different at the 0.05 level of significancecompared to MCC (n = 3). Span Formulation D₁₀ D₅₀ D₉₀ (d₉₀-d₁₀)Acetaminophen 804.1 ± 57.0 1054.1 ± 26.6  1271.4 ± 29.5 467 ± 32^(a)Acetaminophen/ 1071.1 ± 99.5  1723.2 ± 148.2  2060.4 ± 182.9 989 ±88^(b) Tramadol•HCl MCC 663.3 ± 24.2 888.0 ± 11.1 1097.5 ± 6.2  434 ±19^(a)

A significant difference (p<0.05) in span was observed between reference(MCC) or acetaminophen pellets and pellets containingacetaminophen/tramadol.HCl, whereby the latter formulation had a broaderPSD. Furthermore, pellet sizes (D₁₀, D₅₀, D₉₀) of formulations withacetaminophen/tramadol.HCl were increased, possibly due to an increasedsolubility of tramadol.HCl, and thus decreasing solid content of theformulation for the same PVOH concentration. An increased binderconcentration (i.e. PVOH) inside the formulation results into theformation of larger pellets (Garekani et al., 2013).

Pellet morphology was evaluated by means of AR and sphericity (FIG. 4),whereby AR was slightly higher for pellets containingacetaminophen/tramadol.HCl. The mean AR (1.21) was marginally above 1.2which is required for pharmaceutical applications (Krause et al., 2009).A wider distribution for sphericity was detected with a high mean valueof 0.92.

Friability of both formulations was low as for formulations containingacetaminophen and acetaminophen/tramadol.HCl respectively 0.02±0.01% and0.14±0.01%. was obtained. FIG. 5 shows the in vitro dissolution profilesof fixed dose combination pellets with acetaminophen/tramadol.HCl(325/37.5).

Tramadol.HCl was released quickly within 10 min., whereas acetaminophenwas released within 20 min. It was noticed that acetaminophen releasewas faster inside acetaminophen/tramadol.HCl pellets compared to pelletscontaining 70% acetaminophen. This could be explained due to theaddition of tramadol.HCl, which has a high solubility that contributesto a faster disintegration of the pellet.

2.3 Coating

Usually, the drug load of sustained release pellets for highly watersoluble drugs is limited as large amounts of MCC (to enableextrusion-spheronisation) and release retarding polymer are needed. Asthe MCC concentration could be lowered by the addition of PVOH, highquality pellets could be obtained with a metformin load up to 90%. Basedon its high drug content and low friability (0.66±0.03%), formulation 20(F20) was selected for coating trials. Different coating levels wereapplied (Table 4) and the influence on drug release was plotted as afunction of dissolution time. As shown in FIG. 3. (B), release kineticsdecreased in function of coating thickness. Moreover, it was found thata 20% (w/w) coating (percentage based on pellet weight) was able tosustain drug release for 12 h. When coating experiments were performedwith an aqueous solution, the drug on the pellet surface dissolvedfaster. Therefore, it was able to diffuse into the polymer film duringcoating trials and act as a pore-forming agent during dissolutiontesting. This is reduced by using sufficient coating material (>15-20%)or by pre-treating the pellets with talc. The influence of dissolutiontesting on pellet morphology (i.e. surface porosity) was examined viaSEM on coated and uncoated pellets (results not shown). Whereas thesurface porosity of the uncoated pellets increased after 12 hdissolution testing, the morphology of the 20% coated pellets remainedunchanged. For the GlucophageTM SR tablet (Merck Serono), a gel-likelayer was formed around the matrix tablet due to the hydration ofhydroxypropylmethylcellulose and sodium carboxymethylcellulose which areincorporated as release retarding agents.

2.4 Taste Making

As the MCC concentration could be lowered by the addition of PVOH, highdrug loaded taste masked ibuprofen pellets were successfullymanufactured via extrusion-spheronisation whereby the bitter taste ofhigh drug loaded ibuprofen pellets completely disappeared after coating.The effectiveness of the coating was evaluated in healthy volunteers.

2.5 In Vivo

For the pellet formulation, a maximum plasma level of 2.5 μg/mL wasreached 3.5 h (T_(max)) post administration. In case of Glucophage™ SR(½ tablet), a C_(max) value of 2.4 μg/mL was observed 2.8 h (T_(max))after oral intake. The HVD_(T50%Cmax) values were 5.1 and 5.6 h,resulting in R_(D) values of 1.6 and 1.7 for the pellets and Glucophage™SR reference formulations, respectively. Despite the narrow absorptionrange (i.e. mainly upper part of gastro-intestinal tract) of metforminhydrochloride and shorter gastro-intestinal residence time ofmultiparticulate dosage forms, the pellet and tablet formulations didnot have significantly different pharmacokinetic parameters (i.e. AUC,T_(max), C_(max), HVD_(t50%Cmax) and R_(D)). An observation that couldbe explained by the higher sensitivity of the hydrated gel layer (at thesurface of the Glucophage tablets) to gastrointestinal shear forces.This hypothesis was confirmed after in vivo experiments as no residue ofthe reference tablet could be detected in the faeces. In contrast, thegeometric shape of the pellets (which had no residual drug content) wasunaffected.

TABLE 11 Mean pharmacokinetic parameters (±SD, n = 6) after oraladministration of 250 mg metformin•HCl to dogs as pellets andGlucophage ™ SR 500 (½ tablet). According to independent samplet-testing, both formulations did not significantly differ. Cmax TmaxAUC0-12 h HVDt50% Cmax Formulation (μg/mL) (h) (μg · h/mL) (h) RDpellets 2.5 ± 0.2 3.5 ± 1.0 14.5 ± 2.4 5.1 ± 1.4 1.6 ± 0.4 GlucophageTM2.4 ± 0.2 2.8 ± 0.4 15.0 ± 0.9 5.6 ± 0.6 1.7 ± 0.2 SR

PVOH pellets were successfully coated with an acrylic-based sustainedrelease polymer, sustaining drug release from pellets containing 70%(w/w) metformin hydrochloride over a period of 12 h. After oraladministration the in vivo performance of the coated pellets did notsignificantly differ from the commercially available Glucophage™ SRreference formulation (FIG. 6).

3. CONCLUSIONS

This study demonstrates that PVOH solution is a promising pelletisationaid for the production of granules/pellets with high drug concentration(up to 70-90%), since MCC based pellets could only be processed withsatisfactory properties and yield up to a concentration of 50%acetaminophen. Subsequently, those high drug loaded pellets (on thebasis of PVOH) were used to produce a fixed dose combination ofacetaminophen/tramadol.HCl, whereby although pellet quality (span, AR,sphericity and friability) was slightly decreased, in vitro dissolutionprofiles of pellets containing acetaminophen/tramadol.HCl showed a fastdrug release. In addition, the PVOH pellets were successfully coatedthereby sustaining drug release or masking taste. After oraladministration, the in vivo performance of the coated pellets did notsignificantly differ from the commercially available formulation.

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What is claimed is:
 1. A method of preparing a pellet, the methodcomprising: mixing one or more active agents to form a mixturecomprising from 1% to 15% by weight partially hydrolyzed polyvinylalcohol (PVOH) with a degree of hydrolysis between 70% and 95%, and from0.5% to 35% by weight of microcrystalline cellulose (MCC); wetting themixture to form a wet mixture; extruding the wet mixture to obtain anextrudate; spheronizing the extrudate to obtain a plurality of pellets;and drying the plurality of pellets.
 2. The method according to claim 1,wherein wetting the mixture comprises adding PVOH to the mixture as anaqueous solution.
 3. The method according to claim 1, further comprisingcoating the plurality of pellets after drying the plurality of pellets.4. The method according to claim 3, wherein a taste-masking agent isincluded in the coating.
 5. The method according to claim 1, wherein themixture comprises a ratio of PVOH/MCC of from 50/50 to 5/95.
 6. Themethod according to claim 1, wherein the one or more active agents areincluded in the mixing at at least 40% by weight.
 7. The methodaccording to claim 1, wherein the one or more active agents is anantidiabetic agent.
 8. The method according to claim 1, wherein the oneor more active agents is metformin.
 9. The method according to claim 1,wherein at least two active agents are included in the mixing.
 10. Themethod according to claim 1, wherein the extruding is cold extruding.11. A granule or pellet obtained by the method according to claim
 1. 12.The granule or pellet according to claim 11, wherein the the granule orpellet comprises a diameter of from 0.3 to about 3 mm.